1. Field of Invention
This invention relates to fluid-filled bladder-type mattresses such as waterbed mattresses and air mattresses, and particularly to bladder mattresses adapted to suppress undesired lateral and vertical motion of the mattress and undesired fluid wave motion.
Suppression of bed motion is desired in both air and waterbed mattresses. Discomfort, difficulty in movement and nausea may result from excessive bed motion.
Undesired motion is not only a concern in the more conventional applications and use of fluid-filled beds, it is particularly a problem in fluid-filled beds used for emergency purposes where motion of a bed supporting an injured person may aggravate injury.
2. Description of the Prior Art
Waterbed and air mattresses are known wherein motion is suppressed or minimized. Conventional air mattresses comprise, for example, an array of tubular sections formed by bonding the upper surface member to the lower surface member and wherein the sections are in fluid communication through selected constructions. Such a mattress is particularly susceptible to buckling along the bonding ribs, which is undesirable, particularly of an air mattress in emergency or disaster applications where bed movements and buckling may aggravate injury or render transport of a patient more difficult.
The problem of wave motion in waterbed mattresses is well-known. Three techniques are known for wave motion suppression in liquid-filled bladders. The first technique involves use of a fluid other than water which is characterized by a high viscosity and inherent damping characteristics. A second technique involves inclusion of energy absorbing means within the bladder. A third technique involves isolation of the fluid within compartments of the mattress.
All of these techniques exhibit particular disadvantages. The high viscosity fluid is generally expensive and not readily available. Further, the fluid may present a hazard if the bladder ruptures. Still further, the fluid may not be readily disposable.
A popular energy absorbing technique known to the art involves the use of wave motion absorbing cylinders within the bladder. However, undesired gas bubbles tend to be trapped within the cylinders and to be released into the bed, thereby creating gas pockets.
The use of barriers to compartmentalize the fluid is only partially effective. Wave motion can readily propagate through most pliant barriers known to the art. Moreover, relatively rigid barriers detract from the known desirable characteristics of liquid fluid-filled mattress, for example, by creating non-uniformities in the support properties of the mattress. Still further, fully compartmentalized structures require individual filling of each compartment. Therefore, except for bifurcated structures (double twin mattresses) provided with absorbent barriers, compartmentalized structures have not been well received.
What is therefore needed is a mattress structure which is capable of suppressing waves as well as any motion in the mattress structure without detracting from the support characteristics of the mattress.